U.S. Pat. No. 4,071,259, to D. A. Ernest, discloses a parallelogram linkage support for the front wheels of a tractor or the like whereby either of those wheels can rise relative to the other as the vehicle moves over irregular terrain, so that all four wheels maintain ground contact to afford good steering control. The advantage of the arrangement is that the center about which the front wheels effectively swing up and down is at a relatively high elevation, to be above the center of gravity of the vehicle and thus provide excellent vehicle stability.
U.S. Pat. No. 4,416,109, to J. J. Slazas, discloses a mower hitch support for a tractor having a parallelogram linkage front wheel suspension of the type disclosed in the Ernest patent, whereby an underslung mower is caused to tilt laterally in general conformity to tilting of the front tractor wheels, to thereby avoid scalping of the lawn. In this Slazas patent, the power transmitting connection between the mower and an engine that is conventionally mounted on the front part of the tractor frame is disclosed only as comprising pulleys on the top of the mower housing, connected with the mower blade spindles and intended to be driven by a V-belt. The mower obviously had to be driven from a power takeoff that was wholly disposed behind the parallelogram linkage, and there was no provision for powering a front-mounted implement such as a snowblower.
As will be apparent from a glance at the drawings in the Slazas patent, a parallelogram linkage front wheel suspension with a tiltable mower hitch extends both laterally and vertically across a substantial area at the front of the tractor. To transmit power by means of belts from behind that suspension to in front of it--or vice versa--would involve a complicated arangement of pulleys. Futhermore, a belt transmission arranged to provide one or more changes of direction of power transmission, as where there are both horizontally extending and vertically extending belt stretches, is not satisfactory in cases where two or more belts must be used to accommodate high horsepower requirements.